The invention relates to interposer assemblies of the type which are sandwiched between substrates to form electrical connections between opposed pads on the substrates, and to cantilever contacts for forming electrical connections with contact pads.
Interposer assemblies typically include plastic plates with through passages and contacts in the passages for forming electrical connections between opposed contact pads.
Interposer assemblies form electrical connections between contact pads arranged in a very close proximity to each other. The pads may be arranged on a one millimeter center-to-center grid. Each assembly may include as many as 961 contacts with four interposer assemblies mounted in a single frame with a total of 3,844 contacts in the frame. The contacts must establish reliable electrical connections with the pads when the assemblies are sandwiched together between circuit members. Failure of a single contact to make a reliable connection renders the entire frame useless.
Contacts in interposer assemblies include contact surfaces which mechanically engage the contact pads and form electrical connections with the contact pads. Conventional interposer assemblies have single surface contacts which engage each pad to form a single electrical connection with each pad. The contact may wipe along the pad to improve the quality of the electrical connection. Impurities, oxides or contaminants on either the contact surface or the pad can impair the single surface electrical connections with the pads. Contacts used in interposer assemblies are typically symmetrical about the center of the insulating plate, each including a separate spring which biases a single contact surface against a pad.
Accordingly, there is a need for an improved interposer assembly in which each contact makes redundant contacts with each pad so that when the assembly is sandwiched between overlying and underlying substrates each contact establishes two reliable electrical connections with each pad. The connections should have small contact areas to increase the contact pressure between the contact and the pad. Wiped high contact pressure redundant connections would provide reliable interposer assembly electrical connections. There is also a need for a method of making a contact with spaced contact points from strip stock, which may be very thin and difficult to form.
Further, there is need for a spring contact having spaced contact points for engaging a contact pad and forming redundant wiped high pressure redundant electrical connections between the contact and the pad.
The invention is an improved interposer assembly including contacts mounted in passages extending through an insulating plate with each contact having two contact points on each end of the contact. When the interposer assembly is sandwiched between overlying and underlying substrates the pairs of contact points are brought into wiped pressure engagement with overlying and underlying pads and forms redundant electrical connections with the pads.
The contact points are formed on rounded edge corners of the contacts and have small contact areas, resulting in high contact pressure and reliable electrical connections despite debris, oxides and surface contaminants on the contacts and pads.
Each contact includes two tapered spring arms joined to a central portion. A pair of contact points is formed on the outer end of each spring arm. The points project above and below the plate. The arms are independently deflected during compression of the contact by overlying and underlying substrates. The spring arms may include retention legs extending outwardly from the contact points for engagement with adjacent cam surfaces. Compression of the contacts moves the ends of the legs along the cam surface to further stress the spring and increase contact force.
Additionally, the invention relates to a contact having a beam with a mounting end and a contact end carrying a pair of laterally spaced contact points. Movement of a pad against the contact points stresses the beam and moves the contact points laterally along the pad to form wiped high pressure electrical connections between the contact and the pad. The contact points are rounded edge corners and have a very small contact area in order to increase contact pressure and form redundant wiped high pressure electrical connections between the contact and the pad. The contact points are preferably located on opposite sides of the spring arm and stabilize the contact against twisting.
Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings illustrating the invention, of which there are five sheets of drawings and two embodiments.